Multi-ram press and method of metal forming

ABSTRACT

A method of forming a workpiece, including the steps of: providing a center ram, a first outside ram, a second outside ram, and a die; pressing the center rain against the workpiece and toward the die to a first predetermined die depth; trapping the workpiece between the center ram and the die; pressing the first outside ram and the second outside ram against the workpiece and toward the die to a second predetermined die depth; and stretching the workpiece beyond a yield tensile strength of the workpiece material. The die surface has a die center surface which includes at least part of a first arcuate surface, a first planar surface, and at least part of a second arcuate surface. The center ram surface is complimentary in shape to the die center surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a non-provisional application based upon U.S. provisional patent application Ser. No. 60/564,010, entitled “MULTI-RAM PRESS AND METHOD OF METAL FORMING”, filed Apr. 20, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to metal forming, and, more particularly, to the forming of a reflector or reflector housing of a light fixture.

2. Description of the Related Art

Robert Hooke articulated in his 1678 treatise ut tensio sic vis a relationship between elastic deformation and load which is now known as Hooke's law, and which states, in its simplest form, that stress is proportional to strain where stress is the force per unit area in a body and strain is the axial deformation per unit length of the same body. The constant of proportionality is known as the modulus of elasticity, or Young's modulus, where strain=stress/Young's modulus. For common metal materials such as many steels, Hooke's law describes the elastic region of the stress-strain curve associated with a particular steel where a steel body at normal temperature regains its original shape, or springs-back, upon the removal of the stress causing load.

Hooke's law holds up to a point where the material becomes plastic (the point where the deformation (strain) of the material is unrecovered) and this point is called yield tensile strength. The plastic region terminates at the ultimate tensile strength of a material which is the limit stress at which the material actually breaks. In many steel constructions, the maximum allowable tensile stress at any point in the construction is ⅔ of the yield strength of the particular steel in order to provide a margin of safety relative to potential fracture of the material.

In metal forming, there is known an apparatus for a method of bending a channel section workpiece whereby a center projection is moved with a counter pressure plate, with the workpiece in between, against side formations which constrain the piece. A desired double bending or joggle is created with no crinkling or rippling of the member flanges and the extent of displacement of the center section can be selectively adjusted to allow for “spring-back” so that the final shape, when released from the press, is within required tolerances even though the specification of the metal, in particular its yield strength, may vary. However, disadvantages of this apparatus include that it requires seven rams, and a center projection is moved with a counter pressure plate.

Also known is an apparatus for securing a piece of flat sheet metal between two sets of outer vice plates, and center pressure and counterpressure plates whereby the center plates move vertically and the outer plates move horizontally to avoid stretching the piece. A disadvantage of this apparatus is that it is complicated by requiring center plates which move vertically and outer plates which move horizontally.

In another known apparatus there is disclosed a molding die of irregular-shape between a male die and a female die whereby a pin in a male die extend to hold the sheet piece against the female die while side parts shape the piece. Just before the end of the molding, the pins go into the male die and mold the sharply bent parts, and as a result, the sharply bent parts are molded. A disadvantage of this apparatus is that it requires a pin in the male die.

Another known metal forming system includes multiple die forming stations in order to achieve a required final shape of the formed part. Disadvantages of this kind of system include a high capital cost for the multiple die forming stations, increased manufacturing cycle time required by the transferring of the formed part to the multiple stations, and a potential for quality problems in the formed part due to the additional handling and multiple die forming stations.

What is needed in the art is a metal forming apparatus and method which forms a metal part with a minimum of die forming stations, rams and operations, and relatively simple and inexpensive dies and rams.

SUMMARY OF THE INVENTION

The present invention provides a single station method of forming a reflector or reflector housing of a light fixture, or other formed parts, which effectively eliminates spring-back in the formed part.

The invention comprises, in one form thereof, a method of forming a workpiece, including the steps of: providing a center ram, a first outside ram, a second outside ram, and a die; pressing the center ram against the workpiece and toward the die to a first predetermined die depth; trapping the workpiece between the center ram and the die; pressing the first outside ram and the second outside ram against the workpiece and toward the die to a second predetermined die depth; and stretching the workpiece beyond a yield tensile strength of the workpiece material. The die includes a die surface which has a first arcuate surface, a first planar surface and a second arcuate surface, where the first planar surface is interposed between the first arcuate surface and the second arcuate surface. The die surface has a die center surface which includes at least part of the first arcuate surface, the first planar surface, and at least part of the second arcuate surface. The center ram has a center ram surface which includes a center ram first arcuate surface, a center ram planar surface, and a center ram second arcuate surface where the center ram planar surface is interposed between the center ram first arcuate surface and the center ram second arcuate surface. The center ram surface is complimentary in shape to the die center surface.

The invention comprises, in another form thereof, a forming tool for forming a workpiece. The forming tool includes a die which has a die surface with a die center surface, a die first outer surface and a die second outer surface. The die center surface is in between the die first outer surface and the die second outer surface. The forming tool further includes a center ram, a first outside ram and a second outside ram. The center ram has a center ram surface complimentary in shape to the die center surface. The first outside ram includes a first outside ram surface complimentary in shape to the die first outer surface. The second outside ram includes a second outside ram surface complimentary in shape to the die second outer surface.

The invention comprises, in another form thereof, press for forming a workpiece. The press includes at least one guidepost and a forming tool actuatable along the at least one guidepost. The forming tool includes a die which has a die surface with a die center surface, a die first outer surface and a die second outer surface. The die center surface is in between the die first outer surface and the die second outer surface. The forming tool further includes a center ram, a first outside ram and a second outside ram. The center ram has a center ram surface complimentary in shape to the die center surface. The first outside ram includes a first outside ram surface complimentary in shape to the die first outer surface. The second outside ram includes a second outside ram surface complimentary in shape to the die second outer surface.

An advantage of the present invention is that the formed workpiece is formed at a single workstation, which forming operation previously required multiple workstations, and/or multiple die forming stations in a single workstation.

Another advantage of the present invention is that, by eliminating the need for multiple workstations, and/or multiple die forming stations in a single workstation, which each include a press and forming tool, the capital expense is reduced.

Yet another advantage of the present invention is that the manufacturing cycle time for the formed workpiece is reduced.

Yet another advantage of the present invention is that the manufacturing cost of the formed workpiece is reduced.

Yet another advantage of the present invention is that, by eliminating the need for multiple workstations, and/or multiple die forming stations in a single workstation, which each can include a press and forming tool, extra handling of the formed workpiece and transportation of the formed workpiece between workstations is eliminated.

Yet another advantage of the present invention is that, by minimizing the handling of the formed workpiece and transportation of the formed workpiece, the quality of the formed workpiece increases and the quality of the formed workpiece is also more easily controllable.

Yet another advantage of the present invention is that, by eliminating the need for multiple workstations, and/or multiple die forming stations in a single workstation, which each can include manufacturing tolerances and errors associated therewith, the quality of the formed workpiece increases and the quality of the formed workpiece is also more easily controllable.

Yet another advantage of the present invention is that, by eliminating the need for multiple workstations, fewer operators are needed to form the workpiece and/or the operator(s) can spend more time monitoring tooling trends and product quality in order to prevent product defects, for example.

Yet another advantage of the present invention is that press operator training costs are reduced.

Yet another advantage of the present invention is that energy costs associated with forming the workpiece are reduced.

Yet another advantage of the present invention is that overhead expenses associated with forming the workpiece are reduced.

Yet another advantage of the present invention is that work in process inventory associated with forming the workpiece is reduced.

Yet another advantage of the present invention is that required manufacturing maintenance costs associated with forming the workpiece are reduced.

Yet another advantage of the present invention is that maintenance, repair and operations (MRO) inventory costs associated with forming the workpiece are reduced.

Yet another advantage is that the forming tool of the present invention is relatively simple and inexpensive to manufacture and maintain.

Yet another advantage of the present invention is that, by reducing the manufacturing cycle time associated with forming the workpiece, finished goods inventory can be reduced since the manufacturing system is now more responsive to customer demand.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a perspective view of an embodiment of a press and forming tool according to the present invention;

FIG. 2 is a perspective view of an embodiment of a formed workpiece formed using the press and forming tool of FIG. 1;

FIG. 3 is a front, partially fragmentary view of the press and forming tool of FIG. 1 with the workpiece sheetmetal blank inserted between the rams and die of the forming tool;

FIG. 4 is a front, partially fragmentary view of the press and forming tool of FIG. 1 with the workpiece inserted between the rams and die of the forming tool, and with the center ram engaging the workpiece; and

FIG. 5 is a front, partially fragmentary view of the press and forming tool of FIG. 1 with the workpiece inserted between the rams and die of the forming tool, and with the center ram and the outside rams engaging the workpiece.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIGS. 1 and 2, there is shown a press 10 for forming a workpiece 12. Press 10 generally includes at least one guidepost 14 and a forming tool 16 actuatable along the at least one guidepost 14.

Workpiece 12 is shown in its formed or finished state in FIG. 2. Workpiece 12 can be of any bendable material, and particularly can be of a metal material such as steel or aluminum, but the material of workpiece 12 is not limited to metals. In the embodiment shown in FIG. 2, workpiece 12 is in the form of a reflector or reflector housing such as is used in a light fixture, particularly a fluorescent light fixture, but is not limited to such a form.

Shown particularly in FIGS. 3-5, forming tool 16 includes a die 18 with a die surface 20 which has a die center surface 22, a die first outer surface 24 and a die second outer surface 26. Die center surface 22 is in between die first outer surface 24 and die second outer surface 26. A center ram 28 includes a center ram surface 30 complimentary in shape to die center surface 22. A first outside ram 32 has a first outside ram surface 34 complimentary in shape to die first outer surface 24. A second outside ram 36 has a second outside ram surface 38 complimentary in shape to die second outer surface 26.

In one embodiment, die surface 20 further includes a first arcuate surface 40, a first planar surface 42 and a second arcuate surface 44. First planar surface 42 is interposed between first arcuate surface 40 and second arcuate surface 44. Die center surface 22 includes at least part of first arcuate surface 40, first planar surface 42, and at least part of second arcuate surface 44. Die surface 20 further includes a first edge planar surface 46 connected to first arcuate surface 40, and a second edge planar surface 48 connected to second arcuate surface 44. Die surface 20 can also have a third edge planar surface 50 which extends from first edge planar surface 46 at an angle of approximately 90°, for example, but other angles are possible. Fourth edge planar surface 52 extends from second edge planar surface 48, also at an angle.

Center ram surface 30 includes a center ram first arcuate surface 54, a center ram planar surface 56, and a center ram second arcuate surface 58. Center ram planar surface 56 is interposed between center ram first arcuate surface 54 and center ram second arcuate surface 58. First outside ram surface 34 includes a first outside ram arcuate surface 60 connected to a first outside ram edge surface 62. Similarly, second outside ram surface 38 includes a second outside ram arcuate surface 64 connected to a second outside ram edge surface 66.

All of the arcuate surfaces of forming tool 16 can have profiles which are circular, parabolic, elliptical, some combination thereof, and/or other complex curvatures.

Guideposts 14 are as known in the forming processes' art as related to press apparatus.

In use, the method of the present invention is generally shown sequentially in FIGS. 3-5 where FIG. 3 shows the blank of workpiece 12, which can be a sheet metal such as steel, or other bendable materials. The blank of workpiece 12 is placed between die 18 and rams 28, 32 and 36. In FIG. 4, center ram 28 is pressed against workpiece 12 and toward die 18 to a first predetermined die depth 68, which is approximately die center surface 22 plus the thickness of the material of workpiece 12. In FIG. 5, while center ram 28 traps workpiece 12 against die 18, outside rams 32, 36 are pressed against workpiece 12 and toward die 18 to a second predetermined die depth 70, which is approximately die first outer surface 24 or die second outer surface 26, plus the thickness of the material of workpiece 12.

More particularly, the present invention discloses a method of forming a workpiece, including the steps of: providing center ram 28, first outside ram 32, second outside ram 36, and die 18, and particularly with center ram surface 30 being complimentary in shape to die center surface 22; pressing center ram 28 against workpiece 12 and toward die 18 to first predetermined die depth 68; trapping workpiece 12 between center ram 28 and die 18; pressing first outside ram 32 and second outside ram 36 against workpiece 12 and toward die 18 to second predetermined die depth 70; and stretching workpiece 12 beyond a yield tensile strength of the workpiece 12 material using die 18, center ram 28, first outside ram 32 and second outside ram 36.

The method of the present invention can further include the steps of forming workpiece 12 in a shape complimentary to surface 20 of die 18; and eliminating a spring-back in workpiece 12.

While the yield tensile strength of the material of workpiece 12 is exceeded, the ultimate tensile strength of the material of workpiece 12 is not exceeded, thereby avoiding both spring-back in workpiece 12 after forming, and fracture of the material of workpiece 12 thereby achieving the form of workpiece 12 as shown in FIG. 2, for example, in a single press 10 workstation with a single die forming station.

While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims. 

1. A method of forming a workpiece, comprising the steps of: providing a center ram, a first outside ram, a second outside ram, and a die, said die including a die surface having a first arcuate surface, a first planar surface and a second arcuate surface, said first planar surface being interposed between said first arcuate surface and said second arcuate surface, said die surface having a die center surface including at least part of said first arcuate surface, said first planar surface, and at least part of said second arcuate surface, said center ram having a center ram surface including a center ram first arcuate surface, a center ram planar surface, and a center ram second arcuate surface, said center ram planar surface being interposed between said center ram first arcuate surface and said center ram second arcuate surface, said center ram surface being complimentary in shape to said die center surface; pressing said center ram against the workpiece and toward said die to a first predetermined die depth; trapping the workpiece between said center ram and said die; pressing said first outside ram and said second outside ram against the workpiece and toward said die to a second predetermined die depth; and stretching the workpiece beyond a yield tensile strength of the workpiece material using said die, said center ram, said first outside ram and said second outside ram.
 2. The method of claim 1, further including the step of forming the workpiece in a shape complimentary to a surface of said die.
 3. The method of claim 2, further including the step of eliminating a spring-back in the workpiece.
 4. A forming tool for forming a workpiece, said forming tool comprising: a die including a die surface having a die center surface, a die first outer surface and a die second outer surface, said die center surface in between said die first outer surface and said die second outer surface; a center ram including a center ram surface complimentary in shape to said die center surface; a first outside ram including a first outside ram surface complimentary in shape to said die first outer surface; and a second outside ram including a second outside ram surface complimentary in shape to said die second outer surface.
 5. The forming tool of claim 4, wherein said die surface includes a first arcuate surface, a first planar surface and a second arcuate surface, said first planar surface interposed between said first arcuate surface and said second arcuate surface, said die center surface includes at least part of said first arcuate surface, said first planar surface, and at least part of said second arcuate surface.
 6. The forming tool of claim 5, wherein said die surface includes a first edge planar surface connected to said first arcuate surface, and a second edge planar surface connected to said second arcuate surface.
 7. The forming tool of claim 6, wherein said die surface includes a third edge planar surface extending from said first edge planar surface, and a fourth edge planar surface extending from said second edge planar surface.
 8. The forming tool of claim 4, wherein said center ram surface includes a center ram first arcuate surface, a center ram planar surface, and a center ram second arcuate surface, said center ram planar surface interposed between said center ram first arcuate surface and said center ram second arcuate surface.
 9. The forming tool of claim 8, wherein said first outside ram surface includes a first outside ram arcuate surface connected to a first outside ram edge surface.
 10. The forming tool of claim 9, wherein said second outside ram surface includes a second outside ram arcuate surface connected to a second outside ram edge surface.
 11. A press for forming a workpiece, said press comprising: at least one guidepost; a forming tool actuatable along said at least one guidepost, said forming tool comprising: a die including a die surface having a die center surface, a die first outer surface and a die second outer surface, said die center surface in between said die first outer surface and said die second outer surface; a center ram including a center ram surface complimentary in shape to said die center surface; a first outside ram including a first outside ram surface complimentary in shape to said die first outer surface; and a second outside ram including a second outside ram surface complimentary in shape to said die second outer surface.
 12. The press of claim 11, wherein said die surface includes a first arcuate surface, a first planar surface and a second arcuate surface, said first planar surface interposed between said first arcuate surface and said second arcuate surface, said die center surface includes at least part of said first arcuate surface, said first planar surface, and at least part of said second arcuate surface.
 13. The press of claim 12, wherein said die surface includes a first edge planar surface connected to said first arcuate surface, and a second edge planar surface connected to said second arcuate surface.
 14. The press of claim 13, wherein said die surface includes a third edge planar surface extending from said first edge planar surface, and a fourth edge planar surface extending from said second edge planar surface.
 15. The press of claim 11, wherein said center ram surface includes a center ram first arcuate surface, a center ram planar surface, and a center ram second arcuate surface, said center ram planar surface interposed between said center ram first arcuate surface and said center ram second arcuate surface.
 16. The press of claim 15, wherein said first outside ram surface includes a first outside ram arcuate surface connected to a first outside ram edge surface.
 17. The press of claim 16, wherein said second outside ram surface includes a second outside ram arcuate surface connected to a second outside ram edge surface. 